Combined toxicity of microplastics and antibiotics towards aquatic ecosystems: A case study in Beiluo River, China.

Microplastics (MPs) can adsorb antibiotics to form complex pollutants that seriously threaten the health of freshwater ecosystems. However, few studies have examined the combined ecotoxicity of MPs and multiple antibiotics in natural aquatic environments. In this study, we examined the effects of combined exposure to antibiotics and MPs on aquatic community structure in natural settings in the Beiluo River using eDNA analysis. The results revealed that antibiotic pollution in the Beiluo River mainly originates from animal husbandry and agriculture, whereas MPs mainly originate from agriculture and urban sewage. The community structure of aquatic organisms was significantly correlated with the concentrations of antibiotics and MPs and that the combined effects of antibiotics and MPs were highly interpretable for cyanobacteria and phytoplankton. The effect of MPs on antibiotic toxicity is highly dependent on the antibiotic type and MP particle size. These insights highlight that co-exposure to MPs and antibiotics in the natural environment is a common phenomenon and that co-exposure to MPs can alter the toxicological profile of antibiotics. The results enhance our comprehensive understanding of the complex combined effects of MPs and antibiotics on aquatic organisms, emphasising the necessity of informed scientific management of these emerging contaminants.